Beverage cans have been on the market for several decades, undergoing a series of evolutions, such as the progressive passage from a “detachable pull tab,” wherein a closed loop scored section is coupled to a ring tab, to a “push-in tab” type, wherein no element is detached from the can upon opening. Since in both instances an actuating end of a tab must be pulled off the plane formed by the can top end to open a dispense area, such tabs are herein referred to indiscriminately as “pull tabs”.
Rapidly, it appeared that cans comprising a single, dispense aperture lead to a limited dispensing rate and, in particular, to gurgling of the beverage, due to the difficulty for such systems to balance the pressures inside and outside the can upon dispensing. It has been found that providing the can top with a second, vent aperture, spaced apart from the dispense aperture, yielded a much smoother flow of the liquid out of the can, since the pressure inside the can could instantly adapt to the ambient pressure through said vent aperture. Many two-opening can systems were proposed in the art with widely differing opening mechanisms.
U.S. Pat. No. 4,213,538 proposes a can having a can top provided with two score lines forming closed loops defining two areas to be pushed in with a finger or an external tool. An alternative solution is to fix a pull tab to a rivet located between two areas defined by score lines, such that the tab can be tilted both ways to push a first and then a second areas inside the can like a seesaw such as disclosed in U.S. Pat. No. 5,695,085 or U.S. Pat. No. 5,397,014. In some cases, a single pull tab is first pulled up to push in the dispensing area and then pushed back to its initial position and further down to press in the vent area, such as in US2010/0018976, US2011/0056946, WO2009/078738. These systems, however, have the problem that the vent can be accidentally opened in case a pressure is applied onto the tab. To solve this problem, it has been proposed to not align the first and second apertures with the rivet coupling the tab to the can top. This way, after opening the dispensing opening the pull tab must be swiveled about the rivet axis by the corresponding offsetting angle to face the vent area and only then pushed down to press the vent area inside the can such as disclosed in WO2008/023983. In an alternative embodiment, the actuating end of a tab is first pulled up to open the dispense aperture, then swiveled 180° to face the diametrically opposed vent area, the actuating end is pulled up again to open the vent aperture the same way the dispensing aperture was opened, as in U.S. Pat. No. 5,494,184. WO2010/046516 discloses a can comprising a main pull tab and a secondary lever, both fixed to the can top by a single rivet, wherein the secondary lever is brought into puncturing position upon lifting the main pull tab to puncture the dispense area, whereafter the main tab is brought back to its original position, with the secondary lever brought into puncturing position in front of the vent area, which is opened by pressing further down the main pull tab. This system allows to prevent any accidental opening of the vent. All these systems have in common that several movements are required to open both dispense and vent openings, which is rather inconvenient, in particular when the user has only one hand free to open a can.
Solutions for opening both dispense and vent apertures in a single movement have been proposed in the art. U.S. Pat. No. 3,307,737 discloses a single pull tab coupled to a dispense and a vent areas each forming a closed loop. By pulling one free end of the pull tab, the vent is first pulled off the top can, followed by the dispense area. The inconvenient of this rather old system is well known, in that it generates waste which generally ends on the ground and represents both an ecological threat and a source of injuries. CA2280461 proposes to couple with a rivet the ring end of a pull tab to a vent score line forming a closed loop. By pulling up said ring end to puncture the dispense area, the vent area is pulled off the can top. This system has the inconvenient that a strong force is needed to pull off the vent area from the can top with no leverage offered by said design. US2003/0098306 proposes an improvement to the foregoing system by providing a second lever hinged to the main pull tab at the level of the rivet of the vent area, so that the main pull tab is pulled by pulling the second lever, thus yielding a higher couple. WO2004/035399 and U.S. Pat. No. 3,326,406 disclose systems wherein a single pull tab is coupled to the can top with a first rivet and to a vent area with a second rivet. Unlike the preceding systems, here both dispense and vent areas are pushed into the can by pulling up the pull tab at a point forming a triangle with the first and second rivets forming acute angles. The leverage is provided by the altitude of the triangle intersecting the line between the two rivets.
All these efforts to include a vent aperture which can be opened as easily as possible, solved the problem of gurgling and increased the dispensing rate to about 5 l/min, which is about the double of the flow rate obtained with a single aperture can.
The present invention provides a can allowing to increase even further the dispensing rate.